It depends from generation to generation.
Back in the socket A days, there was no reason to go with any board except the NF7 range from Abit.
939 was a mix between Abit, ASUS and Gigabyte, depending on what you wanted.
775 core2 boards seems to be the same. The first Abit 775 boards were pants, but the Quad GT is considered one of the best boards out there, along with the ASUS range.
The gigabytes seem to be slipping as of later (
IMO), but they do seem to be cheaper.
If you're not overclocking, it really won't make that much difference.
The only thing I have 'against' ASUS is their shockingly bad support. BIOS releases take ages, huge bugs in shipping BIOS's, plus I've never seen whats so special about them.
When you weigh up the excellent Abit support (With a UK RMA service if needed!), that includes the ability to buy spare parts, UK tech phone support and BIOS's that are regular its a no brainer for me. Uguru is also brilliant and couldn't imagine going back to a board without it.
I'm not sure why there are so many fans of ASUS - the boards don't seem to overclock any more than the rest of the bunch these days
But at the end of the day, a
lot of it is down to personal preference - Remember that